It is known to those skilled in the art that mining machines serving for exploitation of thin-bed seams may not come out of certain size limits, that is, must be relatively small in height and length because of confined operating space.
There is known a mining machine for extraction of minerals deposited in thin seams. Said machine comprises two drum-type cutting heads arranged on opposite ends of a body coupled with a gantry disposed above a conveyor. The body accommodates adjustable hydraulic supports and two grippers installed on conveyor guides and serving to hold the mining machine in position above the conveyor. Each gripper is hinge-connected to the body by means of levers positioned in parallel to one another and designed to permit vertical movement of the mining machine (cf. British Patent Specification No. 1,521,006, Class E IF, 1978, and FRG laid-open Application No. 2649599.8, 1977).
In the mining machine of the foregoing design, the body is hinge-connected to the grippers through two parallel levers, and the mining machine body position in the horizontal plane depends on location of the common axis of the hinge joints disposed beside the grippers.
The mining machine body and the gripper in set with the parallel levers form a parallel-crank mechanism serving to permit movement of the body in parallel thereof in the vertical direction when the hydraulic supports are extended or retracted.
However, gaps in the parallel-crank mechanism hinge joints may cause displacement of the body from the position parallel to the seam floor, with the result that the mining machine cutting head winning the mineral may leave wedge-shaped seam remains near the seam roof and floor.